Temperature sensors are used in controls of an aftertreatment device for purifying an exhaust gas from an engine, an exhaust gas recirculation (hereinafter referred to as “EGR”) device for partially recirculating the exhaust gas into an intake system, and other elements. When a temperature sensor malfunctions due to its fault or the like, such controls may not be carried out properly.
In light of this problem, there is known a technique in which malfunctioning of a temperature sensor is detected by comparing an estimated gas temperature, which is estimated on the basis of the running condition of the engine, with a sensor value of the temperature sensor (see, for example, PATENT LITERATURE DOCUMENT 1).